(i) Field of the Invention
The present invention relates to a camshaft of an internal combustion engine.
(ii) Prior Art Statement
FIGS. 9 and 10 illustrate an example of a prior art camshaft of an internal combustion engine which is structured so that a metal cam 2 and a shaft 1 are fixedly joined to each other by resin 3. FIG. 10 is a sectional view taken along line X--X of FIG. 9. In both figures, the cam 2 and the shaft 1 are joined through the resin 3, and the relative displacement of the cam 2 and the resin 3 in the axial direction and the rotational direction is limited by a cam-like flange a. Further, the resin 3 is poured around the shaft 1 and into a groove b so that the relative displacement of the shaft 1 and the resin 3 in the axial direction and the rotational direction is limited and the shaft 1 and the cam 2 are fixed to each other through the resin 3.
However, in such a prior art camshaft, since heated resin 3 is poured between the shaft 1 and the cam 2 when the camshaft is manufactured, the resin 3 contracts when the resin 3 is cooled naturally. Consequently, a gap is produced between the outer periphery of the flange a formed of the resin and the cam 1. The contact surfaces of the resin 3 and the cam 2 are worn away due to variation of timing of the cam or knocking in rotation. Further, when the cam is small, i.e. the size of the flange a shown in FIG. 10, a capacity of resin is decreased and a desired torque between the cam 2 and the resin 3 cannot be obtained.